Device for aligning the sheets on the feed table of sheet-fed machines, particularly offset printing presses

ABSTRACT

A mechanism for handling sheets on the feed table of a printing press which includes improved means for separating adjacent sheets fed in overlapping relation in order to insure that each sheet is independently alined and not affected by withdrawal of the leading sheet. A sheet separator head, recessed in the table is provided having a nozzle for directing a jet of air at an angle upwardly against the top, or leading, sheet and having a suction port on its top surface for engaging the bottom or trailing sheet to prevent it from being drawn along by the top sheet when the latter is removed from the table at high speed by the associated gripper mechanism. In the preferred embodiment the head is mounted upon an arm for rocking movement about a transverse axis from a first, or retracted, position in which the head is angled so that the air jet is effective and a second or horizontal, position in which the suction port is effective, the rocking means being synchronized with the arrival of each sheet. In an alternate embodiment, separate sources of pressure and vacuum are provided, utilizing the rocking movement to produce a sequential action.

Elite States atet 1 1 3,870,293 Simeth 1 Mar. 11, 1975 DEVICE FOR ALIGNING THE SHEETS ON Primary E.\'aminerEv0n C. Blunk THE FEED TABLE OF SHEET-FED MACHINES, PARTICULARLY OFFSET PRINTING PRESSES [75] Inventor: Claus Simeth, Offenbach, Germany [73] Assignee: Roland Offsetmaschinenfabrik &

Schleicher AG., Offenbach/Main, Germany [22] Filed: Sept. 20, 1973 [2]] Appl. No.: 399,452

[30] Foreign Application Priority Data Sept. 20, 1972 Germany 2246140 [52] US. Cl 271/231, 271/237, 271/245 [51} Int. Cl. B65h 9/14 [58] Field of Search 271/60, 50, 53,48, 58,

[56] References Cited UNITED STATES PATENTS 2,160,906 6/1939 Reinartz 271/53 2753.184 7/l956 Backhousc 271/60 3,336,026 8/1967 Preuss 271/60 X Assistant Examiner-Bruce H. Stoner, Jr. Attorney, Agent, or FirmWolfe, Hubbard, Leydig,. Voit & Osann, Ltd.

[ ABSTRACT A mechanism for handling sheets on the feed table of a printing press which includes improved means for separating adjacent sheets fed in overlapping relation in order to insure that each sheet is independently alined and not affected by withdrawal of the leading sheet. A sheet separator head, recessed in the table is provided having a nozzle for directing a jet of air at an angle upwardly against the top, or leading, sheet and having a suction port on its top surface for engaging the bottom or trailing sheet to prevent it from being drawn along by the top sheet when the latter is removed from the table at high speed by the associated gripper mechanism. In the preferred embodiment the head is mounted upon an arm for rocking movement about a transverse axis from a first, or retracted, position in which the head is angled so that the air jet is effective and a second or horizontal, position in which the suction port is effective, the rocking means being synchronized with the arrival of each sheet. In an alternate embodiment, separate sources of pressure and vacuum are provided, utilizing the rocking movement to produce a sequential action.

3 Claims, 8 Drawing Figures llm T0 SHEET FEEDER PATENTEU 3. 870.293

sum 2 OF 2 DEVICE FOR ALIGNING THE SHEETS ON THE FEED TABLE OF SHEET-FED MACHINES, PARTICULARLY OFFSET PRINTING PRESSES It is the practice in high speed feeding of sheets in sequence to the impression cylinder of a lithograph press to advance each sheet of an overlapped series independently into engagement with guides at the front of a feed table. This assures that each sheet will be in proper position and alinement for gripping by grippers on the impression cylinder or by swing grippers which transfer the sheet to the grippers on the impression cylinder.

It has been recognized for some time that the accuracy of position and alinement of a given sheet may be affected by the action of the sheet which precedes and overlaps it. It has been proposed that suction be used in an effort to hold the bottom sheet against the effect of withdrawal of the top sheet, as exemplified in prior U.S. Pat. No. 3,336,026. However, it is found that in the case of thin, light stock, particularly where of a porous nature, suction alone does not constitute a cure and, indeed, it is found that suction, acting through the pores of the bottom sheet, may tend to attract the top sheet to the bottom sheet causing them to cling more tightly together.

It is, accordingly, an object of the present invention to provide a sheet separator head for a feed table which is capable of producing a jet of air for blowing the top sheet clear of the bottom sheet and for simultaneously, or in quick succession, applying vacuum to the bottom sheet so that it is prevented from being disturbed as the top sheet is removed at high speed by the grippers on the impression cylinder. As a result, the bottom sheet may be seated in a precise and controlled fashion against the front guides in a perfectly alined position and in readiness for gripping during the successive cycle of the impression cylinder.

It is a related object of the invention to provide a single head capable of applying an upwardly directed jet of air, as well as suction, preferably in overlapped succession so that air fills the space between the two sheets at the time that the suction is applied.

It is another object of the present invention to provide a separator head which is mounted upon an arm swingable about a transversely extending axis so that the head not only moves with the sheets being acted upon but so that the head changes its angular orientation, moving from an upwardly inclined position, for directing the air jet, to a horizontal position for bringing the suction port into action.

It is yet another object of the present invention to provide a separator head which is capable of applying both pressure and suction to successive ones of a series of overlapped sheets but which is so constructed as to preclude clogging of the suction port by means of the paper dust, anti-offset powder and other particles nomical, and which is capable of operating for long periods of time, on new presses and on presses already installed in the field, without especial care of maintenance.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is a elevational diagram showing a mechanism constructed in accordance with the present invention at the retract point of the operating cycle which is timed with the arrival of the junction between the adjacent sheets.

FIG. la is a fragment showing the upwardly tilted head.

FIG. 2 is a diagram similar to FIG. 1 but at a slightly later point in time.

FIG. 3 shows the mechanism at the extreme of its forward stroke and with the bottom one of the sheets in alined position against the front guides.

FIG. 4 is a vertical section taken through the separator head along the line 4-4 in FIG. 5.

FIG. 5 is a top view of the separator head of FIG. 4.

FIG. 6 is a view similar to FIG. 4 but showing a modified separator head.

FIG. 7 is a top view corresponding to FIG. 6.

While the invention has been described in connection with certain preferred embodiments, it will be understood that I do not intend to be limited to the particular embodiments shown but intend, on the contrary, to cover the various alternative and equivalent constructions included within the spirit and scope of the appended claims.

Turning now to the drawings and particularly to FIG. 1 there is shown the lower edge portion of a feed table 10. The table has the usual front guides 11 for receiving the leading edge ofa sheet which is fed down the feed table and for holding it in alined position for pick-up. Adjacent the edge of the feed table is an impression cylinder 12. It will be understood by those skilled in the art that the impression cylinder cooperates with a blanket cylinder which receives its image from a suitably inked plate cylinder. Since such cylinders do not per se form a part of the present invention, only the impression cylinder has been shown. The impression cylinder, it will be understood, has cyclically operated grippers G which engage the leading edge of the sheet. Such grippers need not take the sheet directly from the feed table, however, and it is conventional to use a preor swing-gripper mechanism (not shown) including grippers oscillated on arms about a transversely extending shaft for passing the sheet from the table to the impression cylinder. Reference may be made to the prior art for the non-illustrated elements.

Means are conventionally provided for feeding the sheets downwardly along the feed table in overlapping or shingled relation. Because of this relation, reference may be conveniently made to a top sheet 15 and a bottom sheet 16, the top sheet, as illustrated, being in leading, and the bottom sheet in trailing, relation. Since the sheet feeder which deposits the sheets in the overlapping relation upon the feed table does not per se form a. part of the invention, it has not been illustrated.

It will be understood that all of the moving elements to which reference has been made operate in synchronism with one another driven from the same driving means. The drive, indicated at has a connection 21 to the impression and related cylinders, a connection 22 to the front guide members and a connection 23 to the sheet feeder. Where pre-register guides 11a are employed these, too, are synchronized via a drive connection 24.

In accordance with the present invention a separator mechanism is provided for separating the adjacent sheets to insure that each sheet is independently alined, such separator mechanism including a separator head having a passage terminating in a nozzle which is forwardly faced as well as a suction port which is upwardly faced, the head being operated so that it first applies a jet of air to the underside of the top sheet to separate it from the bottom sheet followed by the bringing of the suction port into engagement with the bottom sheet to tend to prevent the bottom sheet from being dislodged as the top sheet is rapidly whisked out of the way by the grippers on the impression cylinder.

Referring to FIGS. 4 and 5 the separator head indicated at has a horizontal passage 31 which extends downstream of the sheets and which terminates in a nozzle 32. At its inner end the passage 31 is connected to a compressed air supply line 33. The passage 31 has flaring side walls 34 so that the jet produced is of fan shape spanning a rather substantial width of the sheet. While only a single separator head has been illustrated, it will be understood that in a practial case a number of such heads, identical in structure and function, are used spaced at intervals in the width dimension of the sheet. For the purpose of providing downward suction, the top surface 35 of the head, which is preferably flat, is cut out to provide a suction port 36 rearwardly of the nozzle 32 and facing upwardly, substantially at right angles to the passageway 31.

As a result when air under slight pressure is applied to the pressure line 33, via a throttle valve 37, there are two effects: In the first place a generally horizontal jet of air is produced from the nozzle 32. Secondly, the rapid passage of air alongside the port 36, by reason of Bernoullis principle, produces downward suction at a point which is slightly upstream of the path of sheet movement.

In accordance with one of the aspects of the invention, means are provided for causing the pressure and suction to act upon the respectively adjacent sheets and for causing the two effects to occur sequentially although, to the extent desired, in overlapping relation. This is accomplished in the preferred form of the invention by rocking the head so that it is directed angularly upward upon approach of the junction of the sheets so that the air jet therefrom blows the upper sheet 15 clear of the lower, following which the head is restored to horizontal position to couple the lower sheet to the suction port 36 so that the lower sheet is prevented from being affected by the upper one as the upper sheet is drawn away. Turning again to FIG. 1 the head 30 is secured to, and rocked by, a vertical arm 40 which is swingably mounted upon a transversely extending shaft 41. The arm 40 consists of the upper port of a lever of the first class which carries a cam follower 42 at its lower end. The cam follower rides upon a cam 43 which is secured to a transversely extending rotated shaft 44 which is synchronously coupled, by a connection 45, to the drive 20.

The arm 40 upon which the head is mounted, and particularly its driving cam 43, are so phased with respect to the sheet feeder drive connection 23 that when the junction between adjacent sheets approaches the lower edge of the feed table, the head is in its retracted, upwardly tilted condition illustrated in FIGS. 1 and 1a. With the head in such angled position the air jet indicated at 46 has a substantial upward component so that the top sheet 15 tends to be promptly lifted from the lower sheet 16. Not only is the top sheet blown upwardly but a portion of the air from the jet, indicated at 46a, flows between the sheets creating an air blanket isolating them from one another. Because of the upward angling of the head, the vacuum port 36 is not immediately coupled to the bottom sheet.

However, referring to FIG. 2, prompt rotation of the cam 43, transmitted by the cam follower and arm 40, advances the head 30 forwardly in the direction of sheet movement and, simultaneously, swings the head from its upwardly cocked position to a more nearly horizontal position in which, upon passage of the leading edge of the bottom sheet 16, such sheet becomes coupled to the vacuum port which then exerts a retarding effect upon the bottom sheet, so that the top sheet 15 may be whisked away by the grippers while maintaining the bottom sheet under complete control.

As movement of the bottom sheet continues downwardly along the table, the sheet is engaged at its leading edge by the pre-guides 11a. Such pre-guides, per se well known in the art, serve to decelerate the sheet following which they are retracted, so that the leading edge of the sheet is promptly yet gently deposited in contact with the front guide members 15. Such depositing, illustrated in FIG. 3, completes the forward stroke of the sheet movement. It will be understood that with continued movement of the drive 20 the leading edge of the sheet is engaged by grippers, as mentioned above, while the front guides 11 are retracted to an outof-the-way position. Continued movement of the cam 43 serves to swing the arm 40, and the head 30 mounted upon it, back to the retracted, initial position illustrated in FIG. 1. With the completion of the cycle,

the sheet 16 becomes the top" sheet and the succeed ing sheet, indicated at 17, becomes the bottom one to begin a fresh cycle.

While it is one of the important features of the present invention that a single air line 33 produces both an air jet and also vacuum, it will be understood that the invention is not limited to this dual effect and that, if desired, separate pressure and vacuum lines may be used. A separator head having provision for connection of separate lines is illustrated in FIGS. 6 and 7 where similar elements are indicated by similar reference numerals with addition of subscript a. Thus the head, indicated at 30a, has a horizontal passageway 31a terminating in a nozzle 32a. Air under pressure is fed to the passageway via a line 33a. The passageway has, at 34a, the same flaring side walls illustrated in the earlier embodiment. The top surface 35a of the head has a vacuum port 36a. The vacuum, instead of being induced by flow velocity, is separately applied via a line 33b.

The operation of the head 30a is analogous to that previously described. When the head is in its upwardly inclined position, corresponding to FIG. 1, a jet of air is applied to the underside of the top sheet, but the vacuum port 36a is initially ineffective. As the head 30a rocks down into the more nearly horizontal position illustrated in FIG. 2, coupling occurs between the vacuum port 36a and the underside of the sheet 16 to keep the latter sheet under control. Preferably, the suction is of an impositive nature, capable of inhibiting the motion of the bottom sheet without creating any tight connection between the sheet and the separator head. To insure an impositive vacuum connection, an auxiliary or venting passageway 31b (FIG. 6) may be provided in communication with the port 360.

Regardless of which embodiment of head is used, the sequential application of pressure and suction is particularly desirable in the handling of sheets of thin porous material. The application of the air jet, as stated, not only lifts the upper sheet from the lower but insures that there is a blanket or layer of air between them. Thus when suction is subsequently applied, there is no possibility that the top sheet will be drawn downwardly against the bottom one by reason of suction acting through the pores in the bottom sheet. The degree of sequential action and amount of vertical component of the jet may be readily adjusted by adjusting the condition of initial angling illustrated in FIG. 1 which depends, in turn, upon the effective length of the arm 40. The length of the lever arm and throw of the cam, in turn, affects the length of stroke and the velocity of for ward movement. If desired, the center of pivoting 41 may be moved up into the region of the head so as to achieve the change in angle while minimizing the amount of forward movement, the converse condition being equally available.

What is claimed is:

1. ln a sheet feeding means for a printing press, the combination comprising a feed table having front guides and having an associated impression cylinder adjacent the guides and equipped with grippers, means for feeding sheets onto the table in overlapped relation with the top sheet leading and the bottom sheet trailing, a sheet separator head recessed with respect to the table and extended horizontally in the direction of movement of the sheets, said head having a horizontal passageway therein flaring in the direction of motion of the sheets and terminating in a generally horizontally directed nozzle, means for applying pressurized air to the passageway for formation of a jet of air at the nozzle, the upper surface of the head having a suction port rearwardly adjacent the nozzle so that when air is ejected from the nozzle there is produced by the Bernoulli principle downward suction in a direction substantially perpendicular to the jet, means for cyclically rocking the head about a transverse axis timed with the feeding of the sheets so that the head is upwardly tilted with the result that the air jet is directed from the nozzle with a vertical component for blowing the top sheet clear of the bottom sheet and so that the head is subsequently restored to near horizontal position to present the suction port to the bottom sheet so that the bottom sheet is prevented from being drawn along with the top sheet as the latter is removed by the grippers on the impression cylinder.

2. In a sheet feeding means for a printing press, the combination comprising a feed table having front guides and having an associated impression cylinder equipped with grippers, means for feeding sheets onto the table in overlapped relation with the top sheet leading and the bottom sheet trailing, a sheet separator head recessed in the table having a pressure nozzle defined by a passageway which is directed generally forwardly in the head, a source of pressurized air connected to the passageway to create a pressurized jet at the nozzle, means including an upwardly facing suction port extending generally perpendicularly to the passageway for creating suction at the upper surface of the head simultaneously with the pressurized jet at the nozzle, means including a transversely pivoted arm for supporting the head for rocking movement timed with the feeding of the sheets so that upon arrival of a junction between two adjacent sheets the head is in a backwardly rocked condition so that the air jet is directed with a vertical component for blowing the top sheet clear of the bottom sheet and so that as the top sheet is subsequently removed by the grippers on the impression cylinder the head is tilted into more nearly horizontal position for applying the suction port to the underside of the bottom sheet for preventing it from being drawn along with the top sheet.

3. In a sheet feeding means for a printing press, the combination comprising a feed table having front guides and having an associated impression cylinder equipped with grippers, means for feeding sheets onto the table in overlapped relation with the top sheet leading and the bottom sheet trailing, a sheet separator head having a pressure nozzle and a suction port, means for applying pressurized air and suction respectively to the nozzle and port, the pressure nozzle being faced generally forwardly in the direction of sheet travel and the suction port being faced generally upwardly, and means for cyclically rocking the head about a transverse axis timed with the feeding of the sheets (a) so that the head is upwardly tilted upon arrival of the junction between two adjacent sheets so that air is directed from the pressure nozzle with a vertical component for blowing the top sheet clear of the bottom sheet and (b) so that as the top sheet is removed by the grippers on the impression cylinder the head is tilted into horizontal position for applying the suction port to the underside of the bottom sheet for preventing it from being drawn along with the top sheet. 

1. In a sheet feeding means for a printing press, the combination comprising a feed table having front guides and having an associated impression cylinder adjacent the guides and equipped with grippers, means for feeding sheets onto the table in overlapped relation with the top sheet leading and the bottom sheet trailing, a sheet separator head recessed with respect to the table and extended horizontally in the direction of movement of the sheets, said head having a horizontal passageway therein flaring in the direction of motion of the sheets and terminating in a generally horizontally directed nozzle, means for applying pressurized air to the passageway for formation of a jet of air at the nozzle, the upper surface of the head having a suction port rearwardly adjacent the nozzle so that when air is ejected from the nozzle there is produced by the Bernoulli principle downward suction in a direction substantially perpendicular to the jet, means for cyclically rocking the head about a transverse axis timed with the feeding of the sheets so that the head is upwardly tilted with the result that the air jet is directed from the nozzle with a vertical component for blowing the top sheet clear of the bottom sheet and so that the head is subsequently restored to near horizontal position to present the suction port to the bottom sheet so that the bottom sheet is prevented from being drawn along with the top sheet as the latter is removed by the grippers on the impression cylinder.
 1. In a sheet feeding means for a printing press, the combination comprising a feed table having front guides and having an associated impression cylinder adjacent the guides and equipped with grippers, means for feeding sheets onto the table in overlapped relation with the top sheet leading and the bottom sheet trailing, a sheet separator head recessed with respect to the table and extended horizontally in the direction of movement of the sheets, said head having a horizontal passageway therein flaring in the direction of motion of the sheets and terminating in a generally horizontally directed nozzle, means for applying pressurized air to the passageway for formation of a jet of air at the nozzle, the upper surface of the head having a suction port rearwardly adjacent the nozzle so that when air is ejected from the nozzle there is produced by the Bernoulli principle downward suction in a direction substantially perpendicular to the jet, means for cyclically rocking the head about a transverse axis timed with the feeding of the sheets so that the head is upwardly tilted with the result that the air jet is directed from the nozzle with a vertical component for blowing the top sheet clear of the bottom sheet and so that the head is subsequently restored to near horizontal position to present the suction port to the bottom sheet so that the bottom sheet is prevented from being drawn along with the top sheet as the latter is removed by the grippers on the impression cylinder.
 2. In a sheet feeding means for a printing press, the combination comprising a feed table having front guides and having an associated impression cylinder equipped with grippers, means for feeding sheets onto the table in overlapped relation with the top sheet leading and the bottom sheet trailing, a sheet separator head recessed in the table having a pressure nozzle defined by a passageway which is directed generally forwardly in the head, a source of pressurized air connected to the passageway to create a pressurized jet at the nozzle, means including an upwardly facing suction port extending generally perpendicularly to the passageway for creating suction at the upper surface of the head simultaneously with the pressurized jet at the nozzle, means including a transversely pivoted arm for supporting the head for rocking movement timed with the feeding of the sheets so that upon arrival of a junction between two adjacent sheets the head is in a backwardly rocked condition so that the air jet is directed with a vertical component for blowing the top sheet clear of the bottom sheet and so that as the top sheet is subsequently removed by the grippers on the impression cylinder the head is tilted into more nearly horizontal position for applying the suction port to the underside of the bottom sheet for preventing it from being drawn along with the top sheet. 